A typical production process will include the flow of a fluid-like substance through process lines and/or the storing of a substance within process tanks. Sight indicators are commonly installed in such process lines and process tanks for the observation of the contents of the production process. This observation may be accomplished by visual inspections performed by personnel, measurement data gathered by instrumentation, or a combination of both.
A sight indicator will usually be in the form of either a "sight flow indicator" installed in a process line to observe the relevant characteristics of the contents flowing therethrough or a "sight window" installed on a process tank to observe the pertinent parameters of the contents stored therein. These characteristics/parameters may include color, clarity, degree of mixing, liquefaction, formation of voids or bubbles, turbidity, light refraction, and effectiveness of cleaning solutions. With particular reference to a sight window, it is commonly also used to determine significant height dimensions, such as the overall level of the contents stored in the process tank or the location of interfaces between the components of multi-component mixture (e.g. the interface between oil and water in an oil/water mixture or the interface between solids and liquids in a multi-phase mixture).
A sight indicator will usually include a body, an optical unit, and a connection between the body and the optical unit. The body typically includes a process-interfacing portion which is adapted to interface with the production process and an optical unit-interfacing portion which interfaces with the optical unit, via the connection between these components. The optical unit typically includes a viewing portion for viewing the contents of the production process and a body-interfacing portion which interfaces with the optical unit-interfacing portion of the body.
In many industries, such as those concerned with the production of food, pharmaceutical and/or cosmetic products, sanitation requirements impose certain restrictions on the design of sight indicators. These sanitation requirements include the necessity that leakage into the production process be kept at an extreme minimum to eliminate even the possibility of contamination. Such leakage has commonly been discovered in the connection between the body and the optical unit of sight indicators.
Additionally, such sight indicators must usually be designed so that the opportunity for the contents of the production process to become lodged in the components and/or the crevices between the components of the sight indicator is minimized to industry-accepted levels. This design criteria is necessary because lodged particles typically result in the formation of bacteria which could also result in contamination of the contents of the production process. In the past, the connection between the body and the optical unit has been viewed as a prime candidate for such content lodging.
Still further, industries involved in the production of food, pharmaceutical and/or cosmetic products tend to shy away from sight indicators in which there is a tendency towards failure of the components. This tendency is due to the fact that the failure of certain components, such as a glass viewing portion, may result in fragments being introduced into the production process thereby contaminating its contents. Thus the optical unit, as well as the connection between the optical unit and the body, must be designed to minimize the possibility of such failure. Consequently, industries typically demand that sight indicators be tested at pressure which is at least 1.5 times greater than the maximum working pressure of the production process. For example, in a production process having a maximum working pressure of 150 psig (which is typical of most relevant industries), the test pressure of a sight indicator would have to be at least 225 psig.
The spirit of these restrictions, especially those concerned with leakage and lodging, are reflected in industry requirements that components incorporated into a sanitary production process, such as valves, diaphragms etc., interface with the production process in such manner that the interface qualifies as a "sanitary fitting" or "sanitary connection." "Sanitary connection" in this context corresponds to a connection which satisfies generally accepted and approved industry standards, such as those formulated by the International Association of Milk, Food, and Environmental Sanitarians, the United States Department of Agriculture, the Poultry & Egg Institute of America, the Dairy and Food Industries Supply Association, the Dairy Industry Committee, the United States Public Health Service, and/or other organizations addressing similar concerns.
A sanitary connection in a production process is commonly accomplished by either integral connections or connections comprising sanitary clamping, butt-welds or beveled seat fittings. In sanitary clamping connections, sanitary gaskets and corresponding sanitary-gasket grooves are used to form a sanitary connection between the components of the production process. Sanitary gaskets include a substantially flat annular portion and annular projections which are approximately semi-circular in cross-sectional shape and which extend outwardly from opposite surfaces of the flat annular portion.
In contrast to sanitary gaskets, conventional "non-sanitary" gaskets usually consist either of an annular portion which is entirely flat (a "flat" gasket) or an annular portion which is circular in cross section (an "O-ring" gasket). These types of gaskets are usually not acceptable for applications requiring a sanitary connection because they cannot satisfy the necessary sanitary standards. More particularly, when a flat gasket is sandwiched between components of a production process, it has a tendency to undesirably "breath in and out" thereby increasing the chances of leakage, content lodging, and/or contamination. Regarding the O-ring gasket, it, almost by definition, creates a crevice between the sandwiching components in which the contents of the production process may become lodged.
In a typical sanitary connection, a sanitary gasket is sandwiched between two connecting portions each of which contain a sanitary-gasket groove. Such sanitary-gasket grooves are especially designed to accommodate a sanitary gasket. More particularly, a sanitary-gasket groove will include a flat surface for supporting the flat annular portion of the stationary gasket and a channel for supporting the projecting portion of the stationary gasket. Thus when a sanitary gasket is properly sandwiched between two sanitary-gasket grooves, the gasket is firmly held in position (i.e. it will not "breathe in and out") and no crevices are created between the sandwiching components.
According to the present invention, a sanitary sight indicator is provided which includes a sanitary connection between the components of the indicator, namely the body and the optical unit. In this manner, leakage into the production process is kept at an extreme minimum and the contents of the production process will not become lodged in the connection between the body and the optical unit. Additionally, the viewing portion of the optical unit is designed to greatly reduce any tendencies towards failure. In fact, in tests performed on certain prototypes, the indicators demonstrated pressure ratings substantially exceeding 225 psig and thus they could be incorporated into production process having a 150 psig maximum working pressure.
More particularly, the present invention provides a sanitary sight indicator for viewing the contents of a production process. The sanitary sight indicator includes a body, an optical unit, and a sanitary connection between the body and the optical unit. The body includes a process-interfacing portion which is adapted to interface with the production process and an optical-interfacing portion which interfaces with the optical unit. The optical unit includes a viewing portion for viewing the contents of the production process and a body-interfacing portion which interfaces with the optical-interfacing portion of the body. The sanitary connection includes a sanitary gasket having a substantially flat annular portion, and first and second annular projections which are approximately semi-circular in cross-sectional shape and which extend outwardly from opposite sides of the annular portion. The sanitary connection further includes a sanitary gasket-groove in each of the optical unit-interfacing portion and the body-interfacing portion. The sanitary-gasket grooves each include a flat surface supporting the flat annular portion of the sanitary gasket and a channel supporting one of its annular projections.
According to one embodiment of the present invention, the body comprises a pair of head members which are essentially identical and which each include a process-interfacing portion and an optical unit-interfacing portion. The optical unit is made of a rigid transparent material such as borosilicate glass, acrylic or polycarbonate and it includes a cylindrical viewing portion having two body-interfacing portions on opposite ends thereof. The body-interfacing portions may be substantially co-planar extensions of the cylindrical viewing portion, or alternatively these portions may comprise flanged end portions which are integrally molded with the viewing portion. Such a sanitary sight indicator could be incorporated into a production process line as sight flow indicator.
According to other embodiments of the present invention, a window assembly which is disclosed in U.S. Pat. No. 4,961,628 to Herberts is modified and incorporated into a sight indicator as the optical unit. More particularly, the Herberts window assembly is modified so that a sanitary connection may be created between the window assembly, or the optical unit, and the body of the sight indicator. The owner of the Herberts patent is currently obligated to deliver manufactured window assemblies for distribution in the United States, Canada, and Mexico exclusively to the assignee of the present application.
According to one embodiment of the present invention incorporating the Herberts window assembly, the sanitary sight indicator comprises a cross member including two aligned through-flow sections and two aligned transverse sections. The through-flow sections contain the process-interfacing portions and the transverse sections contain the optical unit-interfacing portions. The optical unit comprises a stainless steel frame having a low coefficient of thermal expansion and a viewing portion which is arranged within the frame and which is made of a glass having a coefficient of thermal expansion not greater than that of the frame. The frame includes the body-interfacing portion of the optical unit. Such a sanitary sight indicator could be incorporated into a production process line as sight flow indicator.
According to another embodiment of the present invention incorporating a Herberts window assembly, the process-interfacing portion of the body is adapted to interface with a tank. In this embodiment, the body preferably comprises an integral part of the tank whereby the process-interfacing portion is actually a transition between the optical-interfacing portion and the remainder of the tank. Such a sanitary sight indicator could be incorporated into a production process as a sight window.
According to still another embodiment of the present invention, the process-interfacing portion of the body is adapted to interface with a tank and the body comprises an integral part of the tank. As such, the process-interfacing portion of the body is actually a transition between the optical unit-interfacing portion and the remainder of the tank. The optical unit of this embodiment is similar in shape to the Herberts window assembly, however, both the viewing portion and the body-interfacing portion of the optical unit are made of a transparent material, such as acrylic or polycarbonate. Such a sanitary sight indicator could incorporated into a production process as a sight window.
These and other features of the invention are fully described and particularly pointed out in the claims. The following description and annexed drawings set forth in detail certain illustrative embodiments, however, these embodiments are indicative of but a few of the various ways in which the principles of the invention may be employed.